Fractures of the proximal femur represent a national health problem of crisis proportions. More than 200,000 hip fractures occur annually, resulting in costs in excess of 7 billion dollars annually. While there is growing evidence that certain therapeutic measures such as estrogen replacement can help retard bone loss and thus reduce hip fractrure incidence, some treatment modalities are associated with significant risks. It becomes increasingly important, therefore, to identify those patients at risk of hip fracture so that appropriate therapy can be instituted. New diagnostic imaging modalities such as x-ray computed tomography (CT) could be employed for this purpose if appropriate tissue characterization procedures and biomechanical fracture risk predictors are developed. The goal of this research program is to develop verified biomechanical predictors of hip fracture risk which can be implemented on available CT scanners and used in the diagnosis and treatment of hip pathologies. To address this goal, we will demonstrate (as we have done in the spine) that accurate determination of femoral neck geometries, cortical thicknesses and trabecualr apparent densities can be obtained using quantitative x-ray computed tomography (QCT). We will then show (through finite element modeling studies, strain gage validation experiments and in vitro failure tests) that the QCT data can be used to predict failure loads. Parametric finite element studies will also be used to determine the most important biomechanical parameters (femoral geometry, bone loss, loading type) controlling spontaneous and traumatic fractures of the femoral neck. Prior to proposing future clinical trials of the resulting fractrure risk predictors, we will also address issues of accurate patient positioning and scan location and develop the appropriate analytic software for direct implementation of these methods on CT scanners.